Method for controlling the vacuum generator(s) in a vacuum sewage system

Abstract

Method for controlling one or more vacuum generators ( 1 ) and thereby the vacuum in a vacuum sewage system, in particular controlling one or more liquid ring screw pumps in such system, including beyond the generator/s ( 1 ) one or more tubular collectors or suction pipelines ( 2 ) connected to the vacuum generator and one or more toilets, urinals, grey water sinks etc ( 3, 4 ), connected to the suction pipeline through branch pipelines ( 6 ). The rotational speed of the vacuum generator ( 1 ) is controlled on the basis of the set vacuum requirement.

The invention claimed is: 
     
       1. Method for controlling vacuum generators which create a vacuum in a vacuum sewage system, the vacuum generators being in the form of electrically driven liquid ring screw pumps in such system, including beyond the generators one or more tubular collectors or suction pipelines connected to the vacuum generator and one or more toilets, urinals, grey water sinks connected to the one or more tubular collectors or suction pipelines through branch pipelines, characterised in that the vacuum of the system is maintained and controlled by controlling rotational speed (rpm) of the vacuum generators in relation to a preset vacuum requirement, further comprising controlling the rpm for each of the vacuum generators in the system with a programmable logic controller (PLC), the PLC being programmed to run a first of the vacuum generators until it reaches a set highest rpm and then start a second of the vacuum generators if the vacuum system requires increased pumping capacity. 
     
     
       2. A method for controlling according to  claim 1 , where the vacuum generators are each driven by an electrical motor, further comprising controlling the rpm of the vacuum generators by controlling the rpm for each of the electrical motors in the system with the programmable logic controller (PLC) through a frequency transformer on the basis of signals from a pressure transmitter. 
     
     
       3. A method for controlling vacuum generators and which create a vacuum in a vacuum sewage system, the vacuum generators being in the form of electrically driven liquid ring screw pumps in such system, including beyond the generators one or more tubular collectors or suction pipelines connected to the vacuum generator and one or more toilets, urinals, grey water sinks connected to the one or more tubular collectors or suction pipelines through branch pipelines, characterised in that the vacuum of the system is maintained and controlled by controlling rotational speed (rpm) of the vacuum generators in relation to a preset vacuum requirement, further comprising controlling the rpm for each of the vacuum generators in the system with a programmable logic controller (PLC), the PLC further being programmed to control the rpm for each of the generators when running such that they are run with the same rotational speed, from lower to higher rpm based on the required vacuum, but such that an additional vacuum generator of the generators that was not running is started when more capacity is required and one or more of the generators which are running are running at a maximum required rpm. 
     
     
       4. A method for controlling according to  claim 3 , where the vacuum generators are each driven by an electrical motor, further comprising controlling the rpm of the vacuum generators by controlling the rpm for each of the electrical motors in the system with the programmable logic controller (PLC) through a frequency transformer on the basis of signals from a pressure transmitter.